The most varied electrostatic or combined electrostatic-magnetic arrangements are known in the art for influencing, particularly for focusing a particle beam. In the case of conventional electrostatic lenses arrangements are used with two or more electrodes which are charged with different potentials in order to cause in the space between the electrodes, a field distribution which acts as a lens for the particle beam. In this case the electrodes can be varied in shape and size. There are apertures, ring elements, and electrodes of cylindrical or conical shape. The lens properties such as focus and aberration properties are fixed by the shape and size of the electrodes and the supplied potentials. However, with a limited number of electrodes it is very difficult to generate a complex field distribution.
In the past, therefore, in order to solve this problem multi-electrode configurations have been used, wherein a further parameter is created by each electrode in order to influence the field distribution. The additional electrodes not only necessitate a substantially more difficult mechanical construction but also require additional voltage sources and are therefore very costly.
U.S. Pat. No. 4,126,781 relates to generating shaped electrical fields for use as electrostatic lenses by employing surface currents on resistive materials to shape electrical fields. In particular, this known electrostatic arrangement is applied to improved types of energy analysers with specific application in the field of Secondary Ion Mass Spectrometry.
The object of the invention is to improve the electrostatic arrangement for influencing a particle beam in such a way that a facility for influencing the electrical field distribution is created which is improved over the prior art and which is distinguished by particularly simple and compact production.